The present invention relates generally to building monitoring and control for commercial and residential use. More specifically, the present invention relates to building monitoring and control systems including security, HVAC and other systems utilizing wireless, bi-directional radio frequency communication between master units and remote units. In particular, the present invention relates to remote units having adjustable transmission power for providing communication while conserving power to extend battery life.
Building monitoring and control systems including security systems, HVAC and other monitoring and control systems are in increasing use in both commercial buildings and residential dwellings. For security systems, the increasing use is due, in part, to a long-term perception of increasing crime rates along with increasing awareness of the availability of building monitoring and security systems. For HVAC systems, the increasing use is due, in part, to the desire to reduce heating and cooling costs, and to save energy.
A building monitoring and/or control system typically includes a variety of remote units coupled to detection devices and at least one master unit which typically resides in a central location in the building and can include annunciation functions and reporting functions to another location such as a central reporting service or police department. Remote units have, in the past, been hard wired to the master unit. For example, in a security system, reed switches or Hall effect switches are often disposed near magnets located near doors and door jambs, with a door opening making or disrupting continuity, with the resulting signal being received by the master unit.
In hard wired systems the remote units and the detection devices may be nearly one in the same. For example, the detection device may be a foil trace on a glass pane and the remote unit may be wire terminals with optional signal conditioning equipment leading to a wire pair connected to the master unit. Hard wired units can be installed most easily in new construction, where running wire pairs is easier than in existing buildings. Installing hard-wired systems can be very expensive in existing buildings due, in part, to the labor costs of snaking wires through existing walls and ceilings. In particular, on a point-by-point basis, retrofitting residential dwellings can be expensive because houses are often not designed to be continually changed, as are many office buildings. For example, most houses do not have dropped ceilings and utility closets at regular intervals. Houses can have higher aesthetic expectations than commercial office buildings, requiring greater care in installing and concealing wiring.
Wireless security systems have become increasingly common. Existing systems use radio frequency transmission, often in the 400 MHz range. Wireless systems can greatly reduce the need for wiring between remote and master unit or units. In particular, wireless systems can communicate between the remote units and the master units without wiring. Remote units still require power to operate, and can require wiring to supply that power, which can add a requirement for power wiring where the power had been provided in hard wired systems over the wiring used to communicate between remote units and the master unit. The power requirement can partially negate the wireless advantage of radio frequency units, as some wiring is still required. The power supply wiring requirement is often eliminated with use of batteries. Battery life is largely a function of power consumption of the remote units. The power consumption is dependent upon both the electronics and upon the transmission duty cycle of the unit.
Current wireless systems typically utilize remote units that can only transmit and master units that can only receive. Accordingly, remote units often transmit messages for needlessly long periods, and at higher power levels than is required, as there is no bi-directional capability, and therefore no way for the master unit to acknowledge receipt of the first remote unit message, or a low power message. What would be desirable, therefore, is a bi-directional wireless monitoring system that can acknowledge receipt of a data message or a low power message. What would also be desirable is a bi-directional wireless monitoring system that uses the acknowledge feature to dynamically adjust the remote unit transmission power to minimize power consumption and extend battery life.
The present invention includes a building monitoring and/or control system that includes bi-directional radio frequency links between master and remote units that can acknowledge receipt of a data message or a low power message sent from the remote unit to the master unit. The bi-directional wireless monitoring system may then use the acknowledge signal, or the lack thereof, to dynamically adjust the remote unit transmission power to minimize power consumption and extend battery life. The by-directional radio frequency links also increase the reliability of the communication link. The transmit power level is preferably set high enough to enable adequate communication, but low enough to not be wasteful of battery life. The optimum transmit power may dynamically change over time with the movement of people, furniture, or even walls within the building environment.
In one embodiment, the remote units use the failure of the master unit to provide an acknowledge signal to the remote unit as an indication of insufficient transmit power at the remote unit. The remote unit may increase the transmit power level, and reinitiate the transmission. This may be repeated until an acknowledge signal is received from the master unit, indicating that an optimum power level has been achieved.
In another embodiment, the master unit is able to measure the received signal strength from the remote units. The master unit may then transmit the received signal strength back to the remote units. The remote units can then increase, decrease, or leave unchanged the remote unit transmit power, as appropriate. Alternatively, or in addition to, the master unit may measure the received signal strength and make a decision within the master unit as to what the remote unit should do regarding the remote unit signal strength. The master unit then sends the remote unit a signal indicating that an increase, decrease, or no change in the remote unit transmit power should be applied.
The present invention allows for dynamically adjusting the power level of remote unit transmissions. The dynamic adjustment is preferably automatic, without requiring manual intervention or service calls. The present invention may adjust for movement of people, furniture, and even walls without requiring any human intervention.